(a) Technical Field
The present invention relates to a sound absorbing and insulating material and a method for manufacturing the same, more particularly to a sound absorbing and insulating material obtained by impregnating a polyimide binder into a nonwoven fabric formed of a heat-resistant fiber, having superior sound-absorbing property, flame retardancy, heat resistance and heat resistance, thus being applicable to parts maintained at high temperatures of 300° C. as well as at room temperature and moldability due to the use of the polyimide binder, and a method for manufacturing the same.
(b) Background Art
Noise, as an unwanted side effect of industrial development, causes gradually more damages. Accordingly, various methods have been provided to prevent noise. As a way of such noise prevention, researches for developing new sound absorbing and insulating materials capable of arresting, absorbing or insulating sound are conducted in various ways.
Representative industrial sectors requiring sound absorbing and insulating materials include electric appliances such as an air conditioner, a refrigerator, a washing machine, a lawn mower, and the like, transportation such as an automobile, a ship, an airplane, and the like, construction materials such as a wall material, a flooring material, and the like, and so forth. The sound absorbing and insulating material is required in other various industrial fields, too. In general, the sound absorbing and insulating materials used in industries require, in addition to good sound-absorbing property, reduced weight, flame retardancy, heat resistance and heat-insulating property, depending on their applications. Especially, flame retardancy and heat resistance may be further required for sound absorbing and insulating materials used in engines, exhaust systems, and the like where high temperature of 300° C. or greater is maintained. At present, an aramid fiber, a polyimide fiber and an oxidized polyacrylonitrile (oxi-PAN) fiber are gaining attentions for sound absorbing and insulating materials having superior heat resistance.
In addition, in order to provide functionalities such as flame retardancy, water repellency, and the like to a sound absorbing and insulating material, many sound absorbing materials wherein a nonwoven fabric containing aramid fibers and a functional skin material are stacked have been developed.
For example, Korean Patent Publication No. 2007-0033310 discloses a flame-retardant sound absorbing material wherein a nonwoven fabric layer in which a heat-resistant short aramid fiber and a short thermoplastic polyester fiber are bridged and a skin material layer formed of a wetlaid nonwoven fabric consisting of a short aramid fiber are stacked.
In addition, Japanese Patent Publication No. 2007-0039826 discloses a water-repellent sound absorbing material wherein a nonwoven fabric layer of a heat-resistant short aramid fiber or a blend of a short aramid fiber and a short thermoplastic polyester fiber and a skin material layer treated with a water repellent are stacked.
Further, Japanese Patent Publication No. 2007-0138953 discloses a heat-resistant sound absorbing material wherein a nonwoven fabric layer consisting of a heat-resistant aramid fiber and a skin material layer formed of a fiber sheet containing a heat-resistant aramid fiber are stacked.
Since the sound absorbing materials described above have a structure wherein a skin material layer is laminated on one side of a nonwoven fabric to provide functionalities such as flame retardancy, water repellency and the like, a hot pressing process for integrating the nonwoven fabric layer and the skin material layer is necessary. Consequently, the overall process is complicated and troublesome, and a flame retardant, a water repellent, etc. included as additives may cause production of toxic gases as a result of combustion during the hot pressing process. In addition, deformation of the internal structure of the nonwoven fabric that may occur during the hot pressing process can lead to deterioration of sound-absorbing property.